1. Field of the Invention
This invention relates to a roller for a web-processing machine. In this case said machine can be in particular a machine for producing a fibrous web, in particular a paper web, paperboard web or tissue web. In addition the invention relates to a web-processing machine with such a roller.
2. Description of the Related Art
To guide the web on web-processing machines, provision has been made up to now for arrangements on which in particular guide rollers, regulation rollers and expander rollers are arranged in succession. Such a conventional arrangement is shown for example in FIG. 1 in which a guide roller 54 and an expander roller 56 are arranged in succession upstream from a pair of press rollers 52 looking in the web running direction L. A side view of this arrangement is shown in the left-hand part and a plan view in the right-hand part of FIG. 1.
A disadvantage of these known arrangements are, among other things, their high investment and maintenance costs.
Because of the simple construction of a guide roller, its components are extremely economical. However, it is a disadvantage that the web run can be negatively influenced through compliance of the guide roller.
Expander rollers are used in web-processing machines in order to prevent fold formation or sagging on a running material web by expanding the material web. Also, expander rollers are used to guide apart material webs that are arranged side by side and parallel with each other. Material webs arranged side by side and parallel with each other can be produced by slitting a wide material web for example. Such expander rollers are known for example from DE 199 27 897 A1 and DE 10 2004 045 407 A1.
Expander rollers often include of several individually mounted segments which entail a high level of maintenance and are accordingly cost-intensive. The maintenance costs of such an expander roller generally equal approximately 60% of the new price. Furthermore, the usual expander rollers used hitherto have a very slim construction and an accordingly low load-carrying capacity so that their use as a guide roller is ruled out.
The newest expander roller versions based on high-performance plastics have optimized curvatures. The disadvantage of said versions is however that the constructions in question are not torque-free mounted, meaning that the support of the machine in question, for example a paper machine, is loaded in undesirable manner. In the case of new plants, account must be given to the torques arising, which requires cost-intensive reinforcements. In the case of existing plants, even more expensive auxiliary structures are required.
What is needed in the art is an improved roller of the type initially referred to, with which the previously mentioned problems are eliminated. In this case the roller in question should be able to perform several of the previously mentioned functions simultaneously. In particular the torques introduced into the support should also be reduced to a minimum.